1. Field of the Invention
This invention relates generally to mobile drill rigs for advancing drill rods into the ground and retracting drill rods from the ground. In particular, the present invention relates to a mounting and rotation coupling system for a vibratory drill head for use on a mobile drill rig.
2. Description of the Related Art
A mobile drill rig can be used for many tasks, including: soil core and soil gas sampling, groundwater sampling and testing, geo-technical investigation, geothermal ground loops installation, contaminant logging, grouting, and materials injection. A typical configuration consists of a power unit, drill mast, positioning features (movement fore and aft, drill mast tilt, outriggers, and so forth), drill head, and support hardware (pumps, winch, etc.).
A vibratory drill head is one common technique used for advancing tooling (or “drill string”) into the ground. A typical vibratory drill head (also commonly referred to as a sonic drill head) includes a sine generator as well as a rotation mechanism to rotate the drill spindle. The sine generator imparts vertical vibrations to the drill string it is coupled to, while the rotation mechanism provides the necessary rotation of the drill string. Typical vibratory drill heads operate between 50-200 Hz. Those knowledgeable in the art recognize the elements necessary to produce the vibratory forces from the sine generator. Therefore a detailed explanation of the components and operating principles will not be described herein. Notable variations of vibratory drill heads are described in U.S. Pat. Nos. 3,379,263, 4,553,443, 6,129,159, and 6,739,410, which are incorporated herein by reference.
Harnessing the vibratory forces created from the sine generator has proven difficult. Many unsuccessful attempts have been made to isolate the drill head carriage, rotation mechanisms, and drive components from the sine generator through complex linkages and metal-to-metal sliding contacts. Premature component failure is greatly increased when improper isolation of the sine generator is not achieved.
Prior methods to connect the rotary motion from the rotation mechanism to the sine generator have been explored. One method, as described in U.S. Pat. No. 6,739,410, includes metal-to-metal sliding contacts with forced lubrication at the surface interface. Another method, as described in U.S. Pat. No. 5,409,070, uses blade-like projections and corresponding spaced apart faces positioned radially around the sine generator. These provide vertical movement of the drill string to accommodate the vibrations imparted from the sine generator as well as rotation confinement. However, all current methods for transferring rotary motion to the drill string while coupled to the sine generator are complicated and maintenance intensive.
In addition, prior methods to allow the vibratory drill head to displace vertically have been limited to short distances. One method, as described in U.S. Pat. No. 6,739,410, uses precision disc springs to isolate the vibration forces from the rest of the drill head. Another method, as described in U.S. Pat. No. 5,409,070, uses a pneumatic spring integral to the drill head that acts to cushion the vibration forces. Other methods include the use of a plurality of plate mount shear isolators (sandwich isolators) that allow for minimal vertical displacement. All of the abovementioned methods attempt to keep the drill spindle in a “neutral” position. However, when coupling on and off of the drill string it is desirable to have a drill head that will displace vertically and “float.” This allows the vibratory drill head to couple on and off of the drill string without any preloading of either the drill string or the vibratory drill head.
Therefore, there is a need for an improved mounting system for the components of the vibratory drill head to increase component life and maximize drilling efficiency.